With recent initiatives to decrease the amount of simple carbohydrates in human diet, there is much incentive for development of low-calorie sweeteners. Today, most sweeteners on the market, such as sucralose, aspartame, and saccharin, are chemically derived. An interesting alternative natural sweetener is stevia, derived from the South American perennial Stevia rebaudiana bertoni. The sweetener is about 300 times sweeter than common sugar. What makes stevia special is that it is a natural substance that can be used to replace common sugar, and is not metabolized so it contains no calories.
The sweetness in the stevia plant is attributed to the presence of high intensity sweet glycosides. The two major glycosides found in the leaves and stems of the stevia plant are stevioside and rebaudioside A. The sweet compounds are commonly extracted from stevia and purified to produce a mixture of the two compounds. Stevioside has a bitter aftertaste, whereas rebaudioside A has more intense sweetness and little bitterness. Thus, there is a strong commercial incentive to develop a process for purification of rebaudioside A from stevioside and other sweet glycosides in order to improve the flavor quality.